In the past air conditioning systems for automotive vehicles, temperature responsive means, such as a thermostatic switch or the like for instance, was associated with an evaporator coil of such systems to ascertain the temperature thereof, and the thermostatic switch was operable within a preselected temperature range to control the energization of a clutch mechanism operable generally for effecting the drive of a refrigerant compressor in such system. Thus, the thermostatic switch was connected in the electric circuit controlling the vehicle air conditioning system and operable in response to preselected high and low temperatures at the evaporator coil of such system to effect the deenergization and energization of the clutch mechanism which, in turn, effected the idling and driving of the compressor in such system, respectively. In this manner, the thermostatic switch cycled the vehicle air conditioning system in response to the temperature of the evaporator coil thereof which, of course, was correlative with the temperature of the refrigerant circulated through such evaporator coil by the compressor.
It was also desirable to utilize a high pressure cutout switch and a low pressure cutout switch in the past air conditioning systems along with the aforementioned cycling thermostatic switch. The past high pressure cutout switch was connected in the air conditioning system in pressure fluid communication with the discharge or high pressure side of the compressor. In the event that the fluid pressure at the high pressure side of the compressor rose to a preselected high value, the high pressure cutout switch was actuated in response thereto so as to interrupt the electrical circuit to the clutch mechanism deenergizing it thereby to turn off the compressor. Thus, the high pressure cutout switch was operable to insure that the fluid pressure developed in the vehicle air conditioning system did not exceed a preselected safe high value thereof. In addition to the high pressure cutout switch, it was also necessary to utilize a low pressure cutout switch in the past automotive air conditioning systems which was connected therein in pressure fluid communication with the suction or low pressure side of the compressor. In the event that the fluid pressure at the low pressure side of the compressor fell to a preselected low value, the low pressure cutout switch was actuated in response thereto so as to interrupt the electrical circuit to the clutch mechanism deenergizing it thereby to turn off the compressor. Thus, the low pressure cutout switch was operable to insure that the air conditioning system could not be operated when the fluid pressure therein at the low pressure side of the compressor fell to the preselected safe low value, i.e., for instance if the system should lose its refrigerant charge. At least one of the disadvantageous or undesirable features of the above discussed past automotive type air conditioning system is believed to be that two separate electric circuit control devices, i.e., the high pressure cutout switch and the low pressure cutout switch, were individually employed to provide the separate operating functions of each such switch in such system.